1. Field of the Invention
The present invention relates generally to a substrate sawing process and more particularly to a process for sawing a substrate strip having multi-alignment means thereon.
2. Description of the Related Art
A conventional substrate sawing process comprises an alignment for positioning a substrate strip so as to adjust the position of a saw machine and to arrange the position of the cutting tracks for substrate sawing. As shown in FIG. 1, a substrate strip 100 comprises a plurality of substrate areas 110 which are aligned along the longitudinal direction. A plurality of alignment marks 111 enclose the substrate areas 110 for positioning a saw machine and cutting marks 112 are provided for measuring or predetermining arrangement of the cutting tracks 101 of the substrate sawing process. After the saw machine is positioned and the cutting tracks 101 are arranged, the saw machine saws the substrate strip 100 along the cutting tracks 101 which are defined by the cutting marks 112, e.g. the cutting tracks 101 are imaginary lines created by two outermost cutting marks 112′, shown in FIG. 1. However, in the prior art the saw machine only chooses one alignment mark 111, e.g. the outermost alignment marks 111′ of the substrate strip 100 to define a reference point and utilizes the outermost cutting marks 112′, located around the substrate areas 110, to predetermine the cutting tracks 101 in the first phase and the cutting tracks (not shown) in the second phase.
The substrate strip 100 is packaged in high temperature circumstances and results in an expansion. When the substrate strip 100 returns to normal temperature, shrinkage in all dimensions occurs. However, each strip has variability which results in different amounts of shrinkage of the substrate strips 100 when returning from high temperature to normal temperature. Even if the substrate strips 100 are controlled in the same process and made of the same material, the shrinkage of the substrate strip 100 is still different. Furthermore, in the prior art each substrate strip 100 is not corrected to define the cutting tracks in the first phase and the second phase. Then the saw machine detects the reference point of the alignment of the substrate areas 110 and moves to the predetermined position to cut the substrate strip 100 along the cutting tracks 101. Because the saw machine cuts the substrate strips 100 (which have different shrinkage) by the predetermined cutting tracks 101, the cutting error A of each substrate area 110 adds to the peripheral substrate areas 110 in all dimensions on the substrate strips 100, even though the cutting tracks are predetermined. Therefore, in the prior art the saw machine cannot cut the substrate strips 100 by the predetermined cutting tracks 101 defined by the cutting marks 112 after the substrate strip 100 has different shrinkage.